title: Effect of fatigue loading on the screw joint stability of zirconium abutment.
abstract: OBJECTIVE
  This study evaluated the effect of fatigue loading on the screw joint stability of a zirconium abutment connected to an external hexagon implant in vitro.
  
  
  METHODS
  Fifteen titanium and 15 zirconia abutments of 3 different heights (5, 8, and 11 mm) were connected to external titanium implants with titanium screws. A torque gauge was used to measure the reverse torque values before and after loading. An air cylindrical loading device was used to simulate mastication at a 45-degree angle to the longitudinal axis of the implant.
  
  
  RESULTS
  There were significant differences (P<0.05) before and after the loading of titanium (5mm) and zirconia (5, 8, and 11 mm) abutments.
  
  
  CONCLUSIONS
  Zirconia abutments for external hexagon implants had durability rates similar to those of titanium abutments after repeating load on the reverse torque of the abutment screw, indicating that the zirconia abutment could be reliably used instead of the titanium abutment.
authors.affiliation: Division of Oral and Maxillofacial Implantology, Tsurumi University, School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama City, Japan. tsumita-mitsuyoshi@tsurumi-u.ac.jp
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Tsumita
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kokubo
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Kano
authors.forename: Keita
authors.initials: K
authors.lastname: Sasaki
mesh_terms: D001696:Biomechanical Phenomena; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design / Q000295:instrumentation; D015921:Dental Implants; D003764:Dental Materials; D003799:Dental Stress Analysis; D013314:Stress, Mechanical; D014025:Titanium; D019415:Torque; D015040:Zirconium
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D015040:Zirconium; D014025:Titanium
keywords: External hexagon; Implant; Screw; Zirconia abutment